1. Field of the Invention
The present invention relates to an apparatus for processing image information supplied from a controller, into bit map data which is adapted for use by a display, a printer or other output device and which is stored in memory means, for subsequent use by the output device.
2. Discussion of the Prior Art
When images such as characters and graphic representations are displayed on a display device such as a cathode ray tube (CRT) according to image information supplied from a control section of a computer, the image information is generally processed into corresponding bit map data consisting of a batch of bits which correspond to picture elements available on the screen of the display device. The prepared bit map data is stored in a suitable memory of the computer such as a random-access memory (RAM), so that the bit map data is subsequently applied to the display device. Described more specifically, the image information supplied from the control section of the computer is in the form of vectorial or outline data which represent segments (straight lines and curves) that define an external profile and/or an internal profile of an image such as a character. For instance, a straight segment of an image is represented by a vector defined by a start point and an end point of the segment. The vectorial data is converted into bit map data adapted to display the appropriate images with a predetermined output resolution. The computer determines whether the memory capacity of the empty or vacant area of the memory (e.g., RAM) is large enough to store the obtained bit map data. If the memory capacity required for storing the bit map data is equal to or smaller than the memory capacity of the empty area of the memory, the bit map data is stored in the empty area of the memory.
It is noted that the above-indicated memory such as a random-access memory whose empty area is used as a memory for storing the bit map data is usually used for other purposes, for example, as a working memory for storing in-process data used for a central processing unit, and a text memory for storing the vectorial image information indicated above. Accordingly, the memory capacity of the empty area of the relevant memory may be smaller than the memory capacity required for storing bit map data for a given batch of image information. In this event, an alarm is constituted to indicate the insufficiency of the empty memory area for storing the relevant bit map data, and an operation to store the bit map data is inhibited. Consequently, the bit map data corresponding to the source image information supplied from the control section of the computer is not applied to the CRT or other display device, and the relevant images cannot be displayed.
A similar problem is encountered when images are printed or recorded according to corresponding bit map data which is prepared based on the source image information, since the memory capacity of the empty area of a memory for the bit map data may be insufficient for storing the bit map data.